Power transmission



Plll 25, 1944 R. TWYMAN ET AL 2,347,301

POWER TRANSMISSION Filed April 22, 1940 2 Sheets-Sheet l N& a o W E B O O H M m YWS .l l B L O .C RTOR A. E3 O M /Y l Ea l TD E 8 a NNLL/AN 3 4 EOR Y Ilm 33 VM D T. i." 4 WMM M a E RSW l a l .EO l. L ro 6 LJH .flo n R 2 Y F w 86E Z 2 B O 4 O 4a a m me @1.0. se o l O M, O 8 ro 6 4 April 25, 1944. l L. R. TWYMA. Em 2,347,301

n POWER TRANSMISSION Filed April 22, 1940 2 Sheets-Sheet 2 FIG. 3

BO 2 (0 |4 a a4 aar@ ISE. |88 23 INVENTORS L. RAYMOND TWYMAN,

JESSE R. MOSER 8. Y HOWARD E. ROSE Patented Apr. 5, 1944 UNITED STATES PATENT omer.. l n 2,341,391 i Raymond Twyman, Jesse- R. Moser, and Howard E. Rose, Detroit.l Micht, assignors to Vickers-Incorporated, DetroitlMich., a corporation of Michigan Application April 22, 1940, Serial No. 330,926

(Cl. Gil-52) Y particularly to those of the type comprising two' or more iiuid pressure energy translating devices one of which may function as a pump and another as a fluid motor. e

'I'he invention is more particularly concerned with a power transmission system for use in oil well pumping for operating the type of pump in which a sucker rod string is utilized in the well to operate the pumping plunger or barrel at the bottom of the well. Hydraulically operated well pumping umts of this class have been known for many years and have recently come into more extensive use. Pumping units oi' ythis class provide many advantages over the conventional walking beam type of pump jack, among them hydraulic well pumping units as previously constructed involves the desirability of keeping the clearance volume of the pumping mechanism at the bottom of the well to a minimum. particularly in wells where a large gas content is present in the oil being pumped. It is readilyl understood that any gas entrained -in the oil within the pumping chamber when its volume is at a minimum is under'high compression at the end of a pumping stroke and acts as a resilienty cushion` which must be decompressed on the suctiiifn stroke before any oil can ow into the pumping cheniber. This problem has been solved to .some er;-

being a greater length of Vstroke and consequent e reduction in the-pump losses due to stretching of the sucker rod as well as the advantage ofy more precisely controlled acceleration and de Ic'eleration at opposite endsof the stroke'resulting in longer sucker rod life due to less violent shock imposed upon the sucker rod string at reversal.

Hydraulic pumping units of this class have heretofore been constructed with hydraulic coun- Lterbalancing means either of the air-loaded type or of the weight-loaded type. It has beenffound thatvwith units of the weight-loaded-type the insertiaof the tremendous weight required to counterbalance a long string of sucker rods in a 'deep well presents a serious limitation upon the maxil mum possible speed of operationof the pumping Aoi! the sucker rod is supported lthe pumping mechanism.

tent in the walking beam type of pump jack by the provision of convenient adjusting means between the pump jack and the sucker rod. Hydraulic well pumping units as previously constructed have involved somewhat diflicult and time consuming procedure in making adjustment of the connection between the hydraulic operating mechanism at the top of the well and the sucker rod.

It is an object of the present invention to provide means whereby adjustment of the minimum clearance volume within the pumping chamber at the bottom of the well may be readily made -et the top. of the well.

A further object is to provide means whereby such adjustment ymayv be made while the weight Further objects and advantages of the present invention will be apparent from the following description, reference being had to the accompanying drawings wherein e. preferred form of the present invention is clearly shown.

In the drawings: l Figure 1 is a diagrammatic view of a power transmission system incorporating a preferred der very high pressures and necessitates rather expensive construction in order to withstand the high pressures upon both sides oi the pressure generating means at the same time.

It is accordingly an object of the present invention to provide a hydraulic power transmission system adapted for operating an oil well pump wherein an air-loaded counterbalancing means may be utilized without requiring the application of high pressure to pressure generating means an pumping equipment.

Another problem which nas presented itself in is. drives the form of the present invention.

Figure 2 is a fragmentary cross section of the work motor piston construction illustrated in Fig ure l.

Figure 3 is. a diagrammatic sectional view of the power unit incorporated in Figure 1 showing the internal hydraulic circuit thereof.

Figure 4 is a cross section taken on line 4 4 of Figure 1. i

Referring now to Figure 1, there is shown a well comprising a casing l0 having a pump l2 at the bottom thereof. The latter may be of any conventional type and, for example, may consist of astationary barrel I4 having the usual check valve 'or "stemmer/awe i6 at the bottom and resiviprosahle plunger it having the usual vhydraulically by` central passage and check' valve 22 at the bottom thereof. At the top of the well there is secured to the top of the casing a discharge head 24 having the usual outlet 28 for the discharge of the oil delivered by the well pump. Immediately above the discharge head 24 there is secured a clamp casing 28 having a rod clamp 30 therein adapted` to be tightened by means of two bolts part of chamber 38. A check valve 42 permits free iiow from connection 38 into' chamber 38 when the `piston is below the normal inlet connection. with ai rotary replenishing control valve 44 operable by means of a lever 48 and linkage, later to be described. Thev valve 44 is normally closed and prevents communication between connection 36 and a drainage connection 48 provided `:for draining seepage along the top surface of the end casting 34.

Rigidly secured in the casting 34 is a long operating cylinder 58 having a piston 52 slidably mounted therein. The latter is normally rigidly connected to the sucker rod 54 which extends down through the mechanism previously described and is connected to the pump plunger i8 for operation of'the same. Suitable Vpacking means are 'provided at 55 in the cylinder casting 38 and at 58 in the clamp casing 28 for sealing the operating oil in chamber 38 and the well uid in disf provided with a trip dog '88 pivoted in `a. side wall ofthecasting 58 and having an operating shaft extending outwardly through said wall to con- Vneetl with an` operating lever 10. The lever 0 is iinectedvby means ofv'a link l2 `to 'the lever 4 6 ofthe valve 44. aspr'ing '|2- normally biasing the the piston 52 reaches the upper li'r'nit of its stroke a cam surface 'i6 provided on the'pist'on mecha- -nism contacts' the dog 6'8"*to rotate the levers 'I0 andidclockwise "to the' position illustrated."

The joint between "t'he cylinder 50 andthe 'upper end casting-'58 maybe 'drained =by means of a drain conduity I8 connecting with 'the drain conduit 48. The conduit 'i6 may have an upward .textension'.118for draining anyfl'seepage' past, the

The construction ofthe piston 52 is illustrated in detail in Figure 2 from which it will be seen that the latter comprises a large cylindrical member'having grooves 80 ior'the reception of suitable piston packing means, and, at its upper portion, is provided with a groove 82 surmounted'by a head portion 88. The piston` 52 is provided with a central bore 88 within which the sucker rod 54 is slidably mounted. Suitable packing means at 88 are provided lfor preventing leakage of oil v`The end casting 3d is also provided veniently the cylinder through the bore 86. Also slidably mounted on the sucker rod 54 is a cylindrical member 90 having a groove 92 at its lower end surmounted by a head 94. Suitable packing means at 98 are provided for preventing seepage through-the central bore 98 of the member 90. The member 90 carries rigidly secured thereto'the tubular tail rod` V64 and has a. shoulder |00 which is adapted to abut against the upper end of the casing member 58 to limit the maximum stroke of the piston 52.

Intermediate the members 52 and 98 there is provided a split clamp member |02 the two halves of which are secured together by bolts |04. The internal bore |06 of the member |02 is preferably slightly smaller than the diameter of the sucker rod 54 so that the member |02 may be securely clamped frictionally to the rod 54. The member |02 is provided with shouldered recesses |08 and 0 at its top and bottom ends which intert with the grooves and heads 82-94 and 82-84, respectively, to provide a rigid connection in an axial direction between members 52, |02 and 90 while permitting some slight adjustment in a radial direction of each member relative to the other.

The hydraulic work cylinder mechanism is connected by means of a conduit ||2 communicating with the connection 35 and a conduit 4 communicating with the connection 80 to a hydraulic power and counterbalancing unifJ generally'designated H8. The latter may be remote from the well and is connected with the work cylinder mechanism solely by means of the conduits H2 and ||4. The drain conduit 48 may also connect to the unit i8 which serves in addition as a reservoir for a supply of hydraulic power fluid.

Incorporated in the unit H8 is an air-loaded counter-balance mechanism generally designated ||8 and comprising a closed cylinder I 20 in which a confined body of air or other elastic fluid may be'kept under a predetermined pressure. Con- |20 may communicate through an open conduitv |22 with a conveniently located air bottle |24 for the purpose of providing a larger volume of confined air than the cylinder |20 alone provides. The lower end of the cylinder |20 is provided with a closure wall |30 having a bore |32 through which a piston rod |34 extends. Suitable packing |36 is provided at one end of the bore'l`32. The rod |34 carries at its upper end a piston' |38 reciprocable in theal'cylinder |20-and provides with the Awall 30 a chamber |39 forhydraullc operating fluid which hasfa connection |40 for the inlet and youtlet ofisuch At thelower end the rod'ly34fis provided with a second piston |52. forming lwith fthe wall |30 a second chamber???|43` for operating'iuid which has .a connection |44.in the plate-|30; Secured tothel lower side ofthe plate |30 is va short cylinder |46 Awithin which thepiston |42 islrecipro- Referring now to-Figure 3, the ,internal construction/of the unit1||8 is there illustrated diagrammatically withnparticular .attention to the hydraulic circuitsinvolved. lIt will be seen that the conduit ||2 connects through the interior of the casing of unit H8 with the connection |40 in the plate |30. This connection is permanently open except for a shut-01T valve |48 (Figure 1) outside the unit I8 which may be closed manually when the'unit is shut down, as will later be described. During normal operation the valve |48 is open so that the chamber 38 at the lower end of the cylinder 50 is in.. permanently open com munication with the chamber |30 beneath piston |38. This circuit comprising the conduit ||2 and the chambers 38 and |39 is hereinafter termed a secondary circuit, and itwill be seen that the pressure within the lower end of cylinder 501s and is counter-balanced by the air pressure in cylinder |20. Normally the pressure incylinder |20 is maintained at a value such that it will counter-balance the full weight of the sucker rod string 54 plus a portion, preferably one-half, of the -weight of the oil column carried on the upper either extreme position of its movement, one of the tapered sections gradually closes the correspending pon zu crzle.

transmitted through this circuit to the piston |38 i side of the plunger |8 of the pump at the bottom -|52 may be manually opened atv such times it isv desired to draintheoil from the lower end of cylinder l).h

The conduit ||4 extends 'through a normally open shut-,od valvev |54 (Figure 1) to one port of a rotary piston pump of the reversible type and designated |56. From the other port of the pump |56 a conduit |58 extends to the connection |44 and to chamber |43. Thus there is provided a circuit, termed hereafter the power circuit, ex-

vtendingbetween the .upper endof cylinder 50 and the chamber |43, the power circuit includingthe pump |56 in series therein. The pump |56 may be driven by a suitable electric motor |60 secured to the outside of the casing of unit ||6 and having a belt drive connection |62 for operating a replenishing andsupercharging pump unit generally designated |64. The pump |56 is i of the type having a swinging yoke |66 which may be swung to either side of a neutral position in alignment with the axis of the pump shaft for reversing the direction of flow of iluid delivered j by the pump |56.

The position of the yoke |66 is determined b5- means of a reversing motor generally designated |68 and comprising a pair of cylinders |10 and |12 in which a double-tapered piston |14 is reciprocable. The latter has a rod |16 connected by a link |18 to the yoke |66 and is adapted to swing the yoke between the two extreme positions illustrated in the drawing which are determined by means -of adjustable stopk screws-80. Shifting of the piston |14 is controlled by a pilot .valve |82 of the customary four-way type adapted to selectively connect two ports |84 and |86 either with a pressure oil inlet |88 or with one of two tank outlets |90 and |92.

Conduitsd|84 and |86 lead to inlet ports |94 and.

|96 at the opposite ends of cylinders |10 and |12.

' Suitable check valves |98 and 200 permit free flow into the chambers but prevent return ow out through the ports v|94 and |96. Ports |84 and |86 also communicate through xed resist-- lthrough check valves 2|0 and 2|2 whichn'openl only to iiow out of the respective cylinder chambers. This communication is established through ports 2|4 and 2|6 which are controlled by the tapered portions of piston |14 in such a manner .thatas the yoke I 66 passes through neutral, both ports 2|4 and 216 are closed gradually and then Itwill be seen that shirungo: the .punt valve |82, for example, to the'left into the position illustrated ln Figure 3, admits pressure from port.

|88 to port |86 and through restriction 204 and checkvalve 200 freely into the chamber |12. Piston |14 is accordingly propelled to the left position, when the port 2|4 is again shut oil.

When the pilot valve |82 is shifted to the opposite position -a similar cycle of movement takes place in the rightward direction."

' The shifting of pilot valve |82is controlled in response to movement of the piston rod |34 by means of a pair of tripping cams2|8 .and 220 which are carried by an extension 222 'of the rod |34. These cams are of a conical shape and are adapted to rock a lever 224 clockwise and counterclockwise a't the lower and upper extremes oi' movement of the piston. rod |34. The rocking lever 224 is connected by a link 226 to the operating stem of pilot valve |82. AThe cam 2|8 may be formed integrally with a rod 228 whichis pivotally secured to the extension 222. I The upper portion ofthe rod 228 is screw threaded and carries the cam 220 threaded thereon. The latter has an extension 230 provided with a perforation so that it may slide upon a stationary pin 232 secured by a bracket 234 to the lower end of cylinder |46. The lower end of the rod 228 is provided with splines at 236 and carries slidably' mounted upon the splines a bevel gear 238.

The latter is positioned between the twp arms of a stationary support 240 so as to prevent vertical f movement of the gear 238. A meshing bevel gear 242 is carried vby a shaft 244 mounted in one wall of the casing of unit H6. Th'e rod 244 has a squared head and suitable lock nuts 246 whereby the latter may be manually adjusted to drive the bevel gearing 242 and 238 and may be locked in any adJusted position. Thus it will be seen that v by rotating the shaft 244 from outside the unit ||6 the shaft 226 may be rotated to yscrew the `cam 220 up or down upon thev shaft 228 and thus determine the upper limit of stroke of the piston. rod |34 by. determining the point in such stroke at which the cam 220 trips the rocking lever 224 50 to shift the pilot valve |82 to the right.

Fluid for operating the pump reversing motor J|68 is supplied by a supercharglng pump 248 which forms one unit of the pump |64. The

pump 248 may be of the wellknown rotary vane type having a constant displacement and is pro-lv vided with afsuction conduit 250 and 'a delivery conduit 252. The latter extends through a check valve 254 to an accumulator unit 256. The accumulator comprises a cylindrical chamber 258 in which a piston 260 is reciprocably mounted. suitame springs 2s: urge the piston 2te inward- 1y in. the cyunaer 25s; Beyond 'the check valve 254 a restricted inlet 264is provided from-the A conduit 252 'to the cylinder 258. In dditi reopenedI Likewise, as the piston |14 reaches 75 outlet conduit 266is`prov'ide'd having a cxlliexkl x l mounted relief valve 218 which receives oil delivered by the pump 248 in excess of Vthevolume taken by the conduit 252 and bypasses such excess through the relief valve to a conduit 212. The conduit 212 leads to one port' of a relief valve 214 which provides free communication between conduit 212 and a second conduit 216. The relief valve 214 is adapted to bypass any excess oil to the tank through a conduit 218 whenever a predetermined pressure in conduits 212 and 21S is exceeded. The relief valves 210 .and 214 may be similar to that disclosed in the patent to Harry F. Vickers, 2,043,453. Y y

The conduit 216 leads to a shuttle valve 285 which communicates .by-means of branch conduits 286 and288 with the conduits iid and |58. The shuttle valve is arranged in the well-known manner to shift in response to pressure in one of the conduits 286 or 288 so as to connect the other convduit with the conduit 216 and thus admit supercharging oil from the conduit 21S to whichever of the conduits H4 or 158 happens to be the low pressure conduit at any given time. The conduits I4 and |58 may be connected by means of branch conduits 28|] and 292'with customary relief valves 294 and 286 and with check valves 28S and 388 for the purpose of admitting oil to charge the system before initially operating the same. v

A bypass including a hand-oprated shut-olivalve 302 connects between the conduits 29o and 252 and provides a means whereby the pumping unit may be stopped and started while the motor i60 continues to run. The bypass valve 322 further provides a means for warming up the oil when starting in cold Weather by setting the valve at a partial opening and causing the energy of the pump |56 to be dissipated as heat through the throttling action at valve 302.

The replenishing and supercharging unit it also includes a small plunger pump 38d which takes oil from conduit 252 and delivers it through a conduit 386 to the secondary circuit l i2. This pump delivers oil constantly into the secondary circuit as long as the electric motor is running, but the quantity thus delivered may be very small sollong as it is slightly greater than the maximum leakage out of the secondary circuit.

1n operation; with the system lled with oil and with the motor |58 running, when bypass valve 302 is open, as shown in Figure `3, the pump 156 delivers oil against negligible resistance through conduit 298, valve 392 and conduit 292 back to the pump inlet. With the parts in the position shown .in the drawing and with valve 382 closed, this bypass path is closed and the pump delivery is directed through conduit H4 to the upper end of cylinder 5|). The pump |58 withdraws oil for this purpose from' the chamber 143 through connection |44 and conduit 158, thus effectively transierring oil from chamber |43 to the upper end of cylinder 5U.- The ,piston- 52 accordingly moves downwardly discharging oil from the lower end of cylinder 50 through connection 36 and conduit l2 to chamber |39.

During this stroke the weight of the columnl of well uid is supported on the check valve i6 at the |20 being somewhat higher than the pressure required to support the weight of the sucker rod string 54, it follows that the work which must be done by the pump |55 on this stroke isillthe work required to move the piston l|38 upwardly against the excess pressure in cylindefiil' over and above the'pressure which balances'the weight of the sucker rod 54. e

During the downward stroke the pump 248 is delivering oil through conduit 252 and check valve 25d and resistance 264 to the cylinder chamber 258 of accumulator 256. When the latter becomes :iilled the delivery of pump 248 bypasses over the relief valve 210 and through conduits 212 and 21B to the shuttle valve 284 where it is distributed through conduit 288 to the suction conduit y|58 of pump ,555. The relief valve 214 acts to limit the pressure available in this conduit, and any excess oil above that required to keep the suction circuit of pump |56 completely filled is discharged to tank through conduit218'.

Likewise the replenishing plunger pump 304 delivers a predetermined quantity of oil continuously through the conduit 355 to the secondary circuit |82. This quantity is rather small, but, nevertheless, causes the piston 38 to completeits upward stroke somewhat sooner than the piston 52 completes its downward stroke.

When the piston rod i434 has moved upwardly sufficiently so that the cam 22u contacts the rocking lever 22d, the latter is shited'as is the pilot valve 152 thus transferring the pressure inlet 88 to the port 184 and' connecting port 186 to the tank conduit 492.' Piston 15 accordingly shifts to the right' as previously described, slowing down near neutral position and continuing on to increase the stroke of the pump i5@ in the opposite direction to thatpreviously maintained. The delivery oi oil through the power circuit lid- |58 is accordingly reversed so that oil is withdrawn from the upper end of cylinder and delivered into chamber M3. Thus the piston 52 and sucker rod string 54 move upwardly while the pistons 138 and M2 move downwardly. During this stroke the excess pressure in cylinder i220 above that required to counterbalance the weight of the rod 54 assists the pump 155 and reduces the amount of work otherwise required to lift the entire column of vwell iiuid carried by the check valve 22 and bottom of the` well. e The air pressure'in cylinder 75 plunger it.`

As the piston 52 approaches the top of its stroke the cam surface 1S contacts lever 68 shifting the -levers 18 and 45 and opening the bypass valve :34,

'thus exhausting oil from the secondary circuit 152. The piston 52 accordingly stops its upward .movement somewhat before the pistons 138 and |42 complete their downward stroke, due to the action of replenishing pump 304 so that the pistons |38 and |42 continue downwardly a short distance until cam 2|8 contacts lever 224 to shift the parts into the position shown in Figure 3.

During this interval when piston 52 has stopped and before piston i '12 reaches its lower limit of stroke, the pump i'withdraws oil from the tank through conduit 290 and check -valve 298, since the normal rateof delivery of pump 248 is insuiilcient to supply the full volume of requirements of pump 56. Thus, at this point in each stroke of the mechanism the relative positions ofthe two pistons 52 and |42 are synchronized. The replenishing pump 304 insures by constantly delivering a small quantity of, oil

reaches its lower limit. The by-pa'ss valve 44 stops the, piston 52 when it reaches the upper limit, and thepiston |42 continues downwardly until the cam 2I8 contacm thevlever 224 and reverses pump |56 in the manner previously described. The cycle is again repeated and so on continuously as long as the remains closed.

In installing a pump in a new well with a new set of sucker rods, it .is found that the sucker rods take a permanent stretch over a period of several months, and if,when the pump is initially installed, the sucker rod length is adiusted so that the pump plunger I2 has a small clear-v ance above the standing valve I6, that the rods soon stretch to the point where the plunger is bottoming on the valve IB at each stroke. Such bottoming is easily detected by workers familiar with the operation of such wells, and. by the present construction adjustment can be readily made to prevent such contact while maintaining also a clearance in the pumping chamber. Thus when it is found that the rod has stretched suhlciently to contact' the standing valve, the stroke of piston 52 may b adjusted by means of the screw shaft 244 which adjusts the position o! cam 220 with respect to the piston |42. In this way the upper limit of stroke of piston |42 may be moved downwardly, so to speak, by moving the' cam niupwardly.

Since the stroke oi' piston 52 is synchronized with that of piston |.42 at the top of the stroke of the latter, it follows that by dropping the upper limit of stroke of piston |42 the lower limit oi' stroke of piston 52 is correspondingly raised while the upper limit thereof remains xed. In this way small adjustments can be made from time to time to compensate for permanent stretch of the sucker rods by merely giving the shaft 244 a partial turn or more. This adjustment may be made while the entire weight of the sucker rods by-'pass valve A302 piston and tail rod assembly may be lowered on the sucker rod by an amount which is considered sumclent to enable the full stroke capacity of the pump unit to be utilized.l It will be noted that, during the time the clamp |02 is loosened,

the tail rod assembly is connected with the piston 'independently of the sucker rod by means ofthe grooves 82 and '92 coacting with the heads 84 and 94. The clamp |02 may be again tightened and the apparatus reassembled.

Thereafter, withvthe valves |48 and |52 again opened and closed, respectively, with the adjust ing rod 244 restored to its original position, and

with the clamp 30V/again loosened, the apparatus it is to be understood that other forms might be adopted, all coming within the scope of the claims which follow- What is claimed is as follows:

l. In a hydraulic pumping system for an oil 1 well having a sucker rod string extending to the top of the we1l,. the combination of hydraulic work ram means connected to the sucker is supported hydraulically by the piston 52 and without disassembly of any of the parts of the apparatus and, in fact, may even be made while the pump unit is in continuous operation.

It will benoted, of course, that as each such adjustment is made the total stroke of the piston 52 is shortened, and since it is desirable to maintain as long a stroke as possible, it i`s found expedient, after a certain amount of the sucker rod stretch has been taken up by adjusting the rod 244, to take time to adjust the piston 52 on the sucker rod 54 so as to again utilize the full stroke capacity of the hydraulic pumping apparatus. When the stroke has been suiiiciently shortened to justify making such an adjustment, the apparatus may be shut down with the piston rod string, hydro-pneumatic counterbalancing means, a closed coupling circuit connecting the counterbalancing means in free communication with the work ram means, a powercircuit. operatively connected with at least one of `said means, distinct from the coupling circuit and includlng a pressure generating means arranged to cause displacement 'of uid ln'either direction through the power circuitgmeans for reversing the iiow of iluid delivered in the power circuit by the pressure generating means and responsive to the volume of fluid displaced into or out of the counterbalancing means, said reversing means being adjustable to vary-one limit of such volume, replenishing means for the secondary circuit, and valve means controlled by thel Work ram means at one limit of its stroke for control- 52 preferably at or nearthe top of its stroke. 'I'he sucker rod may then be clamped to the cas-` ing by tightening p the screws 32, andafter this is done the shut-off valve |48 may be closed and the by-pass valve |52 opened to relieve the oil under pressure beneath the piston 52. Thus the Weight of the sucker rod string is transferred from the piston 52 to the clamp 30.

The Upper structure of the pumping cylinder may then be disassembled by removing the closure tube 56 and the end casting 52 after which the cylinder tube 50 may be lifted upwardly oi from the piston 52. A suitable chain fall or other hoisting mechanism may therbe attached to `the upper-end of tube 64 to support the latter and the-piston 52 against falling'downwardly on the sucker rod 54. The clamp member |02 may then ling the replenishing means to keep said one limit of its stroke at a substantially xed point whereby the other limit thereof may be determined by adjustment of said reversing means. t

2. In a hydraulic pumping system for an oil well having a sucker rod string extendingto the top of the well, the combination of a hydraulic motor comprising a cylinder supportedat thetop of the well, a piston reclprocable in the cylinder and having a central bore, clamping meansabove the piston engageable with the sucker rod and supporting the weight thereof on the piston for securing the latter to. the sucker rod in various longitudinal positions of adjustment,l a tubular c tail rod surrounding the sucker rod above the clamping means, means associated with the clamping means for connecting the tail rod with the piston independently of the sucker rod, and I means forming a duid-tight enclosure 'at the upbe loosened on the sucker rod 54, and the entire 7B' per end of the cylinder and engaging said tail rod with a sealing it, said last means extending above the cylinder and being removable to expose the clamping means lwhile leaving the piston in the cylinder. 4 i

13. In a hydraulic pumping system for an oil well having a sucker rod string extendingto the top of the well, the combination of double-acting l `hydraulic work ram means connected to the sucker rod, means for counterbalancing the 4sucker. rod weight plus a portion of the producing oil column weight, said counterbalancing means comprising three expansible chambers, piston means interconnected with each other to placeV the fluid pressure in two of said chambers in opposition to the iiuid pressure in the third chamof the work ram' means with the other of said two chambers, and a secondary circuit connecting vthe other side of the work ram means with the third chamber.

4. In a hydraulic pumping system for an oil well having a sucker rod string extending to the top of the well, the combination of .hydraulic work ram means connected to the sucker rod String, air-loaded hydraulic counterbalancing means including a pressure chamber having a piston therein, a closed coupling circuit connect- :ing said piston with 'the work ram means, pressure generatng.means effective to deliver fluid alternately in either direction; and means forming a power circuitI isolated from the coupling circuit and including said generating means, said power circuit including oppositely acting ram areas, .one of which is mechanically connected to said piston to dispiace fluid in the coupling circuit.

L. RAYMOND TWYMAN.

JESSE R. MOSER..

HOWARD E. ROSE. 

